Using a tablet is definitely going to limit you in the USB department. I had an Acer Iconia tablet for a while. The charging port was separate from the micro-USB, but the screen quality sucked. Hopefully some other users can provide some suggestions for using a tablet and all of the USB devices you want to use. DriveLine has a screen to display Sensors, including TPMS.
As for the playlist and internet radio, now that I think about it, the version I uploaded yesterday may have had a web-radio station or two in the playlist. Just go into the playlist window and hit the X to clear the playlist. Internet radio stations are handled like regular music files, so they show up in the playlist. I'm not familiar with Subsonic, but if it provides you with a playlist file (.ASX, .PLS, etc) you can add that to the playlist in DriveLine. If Subsonic does not provide you with a playlist file but it does give you a URL, then you can edit the WebRadio XML file in the Settings folder to add the URL. Internet radio is a new addition to DriveLine, so I'm still working on making it easier to use.